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/*
* Mach Operating System
* Copyright (c) 1991,1990,1989 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
/*
* This module maintains information about the presence of
* pages not in memory. Since an external memory object
* must maintain a complete knowledge of its contents, this
* information takes the form of hints.
*/
#include <mach/boolean.h>
#include <kern/zalloc.h>
#include <vm/vm_external.h>
#include <mach/vm_param.h>
#include <kern/assert.h>
boolean_t vm_external_unsafe = FALSE;
zone_t vm_external_zone = ZONE_NULL;
/*
* The implementation uses bit arrays to record whether
* a page has been written to external storage. For
* convenience, these bit arrays come in two sizes
* (measured in bytes).
*/
#define SMALL_SIZE (VM_EXTERNAL_SMALL_SIZE/8)
#define LARGE_SIZE (VM_EXTERNAL_LARGE_SIZE/8)
zone_t vm_object_small_existence_map_zone;
zone_t vm_object_large_existence_map_zone;
vm_external_t vm_external_create(size)
vm_offset_t size;
{
vm_external_t result;
vm_size_t bytes;
if (vm_external_zone == ZONE_NULL)
return(VM_EXTERNAL_NULL);
result = (vm_external_t) zalloc(vm_external_zone);
result->existence_map = (char *) 0;
bytes = (atop(size) + 07) >> 3;
if (bytes <= SMALL_SIZE) {
result->existence_map =
(char *) zalloc(vm_object_small_existence_map_zone);
result->existence_size = SMALL_SIZE;
} else if (bytes <= LARGE_SIZE) {
result->existence_map =
(char *) zalloc(vm_object_large_existence_map_zone);
result->existence_size = LARGE_SIZE;
}
return(result);
}
void vm_external_destroy(e)
vm_external_t e;
{
if (e == VM_EXTERNAL_NULL)
return;
if (e->existence_map != (char *) 0) {
if (e->existence_size <= SMALL_SIZE) {
zfree(vm_object_small_existence_map_zone,
(vm_offset_t) e->existence_map);
} else {
zfree(vm_object_large_existence_map_zone,
(vm_offset_t) e->existence_map);
}
}
zfree(vm_external_zone, (vm_offset_t) e);
}
vm_external_state_t _vm_external_state_get(e, offset)
vm_external_t e;
vm_offset_t offset;
{
unsigned
int bit, byte;
if (vm_external_unsafe ||
(e == VM_EXTERNAL_NULL) ||
(e->existence_map == (char *) 0))
return(VM_EXTERNAL_STATE_UNKNOWN);
bit = atop(offset);
byte = bit >> 3;
if (byte >= e->existence_size) return (VM_EXTERNAL_STATE_UNKNOWN);
return( (e->existence_map[byte] & (1 << (bit & 07))) ?
VM_EXTERNAL_STATE_EXISTS : VM_EXTERNAL_STATE_ABSENT );
}
void vm_external_state_set(e, offset, state)
vm_external_t e;
vm_offset_t offset;
vm_external_state_t state;
{
unsigned
int bit, byte;
if ((e == VM_EXTERNAL_NULL) || (e->existence_map == (char *) 0))
return;
if (state != VM_EXTERNAL_STATE_EXISTS)
return;
bit = atop(offset);
byte = bit >> 3;
if (byte >= e->existence_size) return;
e->existence_map[byte] |= (1 << (bit & 07));
}
void vm_external_module_initialize()
{
vm_size_t size = (vm_size_t) sizeof(struct vm_external);
vm_external_zone = zinit(size, 16*1024*size, size,
0, "external page bitmaps");
vm_object_small_existence_map_zone = zinit(SMALL_SIZE,
round_page(LARGE_SIZE * SMALL_SIZE),
round_page(SMALL_SIZE),
ZONE_EXHAUSTIBLE,
"object small existence maps");
vm_object_large_existence_map_zone = zinit(LARGE_SIZE,
round_page(8 * LARGE_SIZE),
round_page(LARGE_SIZE),
ZONE_EXHAUSTIBLE,
"object large existence maps");
}
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